This invention relates to a sludge de-watering plant having a plurality of filter presses connected in parallel.
As is well known, de-watering plants for mineral sludge or sewage sludge require considerable installations for a high capacity throughput. The quantities of sludge supplied are so large that frequently the task cannot be performed with only one press whereby at least two, but usually more, presses are required. This has the advantage of greater flexibility for a fluctuating supply of sludge, and greater service reliability, because if one press breaks down the remaining presses can continue to operate.
It is customary to provide each press with a particular charging device. Due to the fact that the charge volume at the beginning of the filter process at low pressure is very great, it has been proposed to employ two pumps per press, one of which is designed as a low-pressure pump with a high delivery rate and the other as a high-pressure pump with a low delivery rate. When the maximum adjusted pressure is attained at the low-pressure pump, the low-pressure pump is switched off and the high-pressure pump is switched on. The high-pressure pump is in the form of a variable-delivery pump because of the further decrease in filter capacity towards the end of the filtration.
To enable the press to be filled rapidly at the start of the filter charge, it has also been proposed to provide in the charge pipe a reservoir tank in which sludge is stored under pressure during and/or after the filtration, whereby the press can be filled with such sludge in a short time.
Heretofore, if it had been proposed to apply the filtration system to multiple-press plants, then the outlay for apparatus would be enormous. Also, the utilization factor of the charging units associated with each filter press would be very poor and the overall economy low.